1. Field of the Invention
The present invention relates to an inverter for driving lamps used for a backlight unit of a liquid crystal display (LCD), and more particularly, to an LCD backlight inverter, which can perform a protection operation by monitoring the state where all lamps are separated from their respective lamp connectors (hereinafter, also referred to as “All Lamp Connectors Open”), thereby preventing damage to internal components and circuits, including the lamps.
2. Description of the Related Art
In general, liquid crystal displays (LCDs) include backlights. The backlights may illuminate the LCD from the back of a display panel, which is unable to emit light by itself. Cold cathode fluorescent lamps (CCFLs) have been in common use in backlights for large LCDs, and require the use of an inverter for the operation thereof.
Maintaining even LCD lighting is a critical factor in the driving of the backlight lamps. To this end, the inverter employs a circuit that feeds back the current of the lamp in order to achieve constant lamp current. In addition, the inverter also includes an over-voltage protection circuit that serves to protect the lamps and the inverter circuit when excessive voltage is applied thereto.
The function as a protective circuit is very important for the inverter that drives the LCD backlight unit. Particularly, protecting devices upon the detection of an open lamp is one of the main functions of an inverter that drives multiple lamps.
The related art LCD backlight inverter employs a configuration that detects operating voltages of opposite phases being applied to a plurality of lamps. Thus, the inverter detects the opening, that is, the separation of some of a plurality of lamps by detecting the voltage resulting from unbalanced operating voltages occurring when some of the plurality of lamps are open, thereby performing a protective operation.
However, the related art LCD backlight inverter fails to recognize the state where all of the lamps are open (i.e., All Lamp Connectors Open) because unbalanced operating voltages are not generated in this state. For this reason, while no protective operation is enabled, the inverter performs a control operation to increase the operating current, which is currently at a low level due to the state of All Lamp Connectors Open. Consequently, the operating voltage is applied with a low switching frequency, damaging internal components and circuits, including the lamps.